I tend to believe that the best interfaces have already been made. Behaviourally, CDE is the best and most consistent interface ever made. It looked like ass, but it always did exactly as you told it to, and it never did anything unexpected. When it comes to looks, however, the gold standard comes from an entirely different corner - Apple's Platinum and QNX' PhotonUI. Between all the transparency, flat-because-it's-hip, and stitched leather violence of the past few years, one specific KDE theme stood alone in bringing the best of '90s UI design into the 21st century, and updating it to give everything else a run for its money. This is an ode to Christoph Feck's Skulpture.

I'm a long time KDE user, and I've been tweaking KDE themes (specially colours) for a long time. I just installed this wonderful theme, and it gets what I have been searching for years. Why isn't this theme installed as an optional theme by default in distros??

KDE already have a set of extra themes that ship with KDE full, but the author needs to request to have added to the kdeartwork module. It is considered impolite to begin including other peoples work without their concent, but you could write to the author and suggest it, and even offer to make the request for him.

Anyway, additional themes like this are already automatically available via the built-in Get New Stuff, so it is already pretty easy to find and install.